Splitter knife



INVENTUR Edward M Key BY @LCQCQN Hgen-f United States Patent Thisinvention pertains to wood cutting tools, and relates particularly to asplitter knife of improved construction.

In the production of finished lumber, wherein one stage of operationinvolves the planing of rough cut lumber to smooth surfaces on allsides, it is a general practice, when desired, to split the lumber intotwo or more boards of narrower width. As an illustration, a. quantity of-rough 2" x 12" dimension may be processed through the planer to producefinished-lumber which, for example, is third grade. However, thecharacter of the lumber may be such that it could produce a third grade2" x 8" and a first grade 2" x 4". Thus, greater value may be derived bysplitting. As another illustration, it is a general practice in many sawmills first to cut all logs to 2" x 12" rough dimension and then tosplit and finish them into three 2" x 4", two 2" x 6", or one 2" x 8"and one 2" x 4", whichever is desired for sale.

Whatever is the purpose of splitting, it is apparent that if the boardis split before planing, the lineal footage of lumber to be processedthrough the planer is'doubled and the cost of producing the finishedlumber-is increased proportionately. It is most desirable, therefore, tosplit lumber after planing.

Since the splitting of planed lumber with a conventional saw bladeproduces rough surfaces defining the kerf, and thus would necessitatereprocessing through the planer, attempts have been made heretofore toprovide a splitter knife which would perform the splitting operationwhile simultaneously producing smooth finished surfaces defining thekerf. Such splitter knives as have been employed and proposed heretoforehave not been satisfactory, for the following reasons: 1 v

Splitter knives heretofore have failed to produce kerf surfaces free ofscratches, regardless of their degree of sharpness. This fact hasresulted in such general dissatisfaction with plit lumber that manypurchase orders specifically rule against it. Moreover, such splitterknives have failed to maintain a sufliciently sharp cutting edge for apractical period of time. Under normal operating conditions it has beenfound that such knives require resharpening after about one hour of usein order to maintain the production of kerf surfaces of even minimumsatisfactory smoothness. Thus, since it is economically unfeasible tointerrupt production so frequently, it'has been the practice heretoforeto continue the use of such dulled spliter knives notwithstanding thefact that the lumber thus produced is unsalable at the price of itsgrade. Still further, the use of splitter knives heretofore has requireda feed rate of lumber substantially less than the feed rate permissiblefor other sawmill operations.

It is a principal object of the present invention to provide a splitterknife which is capable of splitting lumber efiiciently whilesimultaneously producing kerf surfaces which are as smooth as can beproduced by the best planers.

Another important object of this invention is to provide a splitterknife which is capable of producing consistently smooth kerf surfacesfor substantially longer periods of continued use than has been possibleheretofore.

Still another important object of this invention is to provide asplitter knife which is capable of producing consistently smooth kerfsurfaces at a lumber feed rate substantially greater than that withsplitter knives of prior construction.

A further important object of the present invention is to provide aspliter knife which, although requiring far less frequent sharpeningsthan splitter knives of prior construction, is capable of beingsharpened with speed, facility and precision, thus reducing the time ofinterrupted production to a practical minimum.

Still another important object of the present invention is to provide asplitter knife which is of economical construction and which is capableof extended use with a minimum of maintenance and repair.

The foregoing and other objects and advantages of this invention willappear from the following detailed description, taken in connection withthe accompanying drawing, in which:

Figure 1 is a view in side elevation of a splitter knife embodying thefeatures of the present invention;

Figure 2 is a view in rear end elevation of the splitter knife shown inFigure 1; and

Figure 3 is a top plan view of the splitter knife shown in Figure 1.

The splitter knife of the present invention includes a shank end 10adapted for attachment to a splitter knife head (not shown), inaccordance with conventional practice. Thus, the shank is provided witha transverse elongated opening 12 adapted to receive a securing bolt forreleasable attachment to a splitter knife head. One side surface of theshank is provided with serrations '14 which correspond withcomplementary serrations on the splitter knife head, whereby to provideadjustable but positive interconnection between the splitter knife andthe head.

Extending from the shank is the splitter knife blade 16. The blade iswedge shaped in transverse cross section, being thinner at its trailingedge 18 than at its leading edge. The leading edge is provided with alongitudinal arcuate grove 20 which preferably extends the full length 1of the blade, whereby to provide laterally spaced cutting edges 22, 24defined by the lateral sides of said leading edge.

The outer end of the blade is formed with a pair of offset,substantially parallel edges 26, 28. The upper edge 26 extends forwardlyfrom the trailing edge 18 of the blade and the lower edge 28 extendsrearwardly from the leading edge of the blade. These otfset edges areinterconnected by an intermediate arcuate edge 30, which forms anundercut below the upper edge. Thus, the forward end of the upper edgeis formed as a saw tooth 32. Since the saw tooth projects radiallyoutward beyond the outermost end of the leading edge of the blade, itfunctions to make the initial cut in a board, as explained more fullyhereinafter.

As illustrated in Figure 1 of the drawing, the length of the splitterknife blade is greater than the thickness of a board 34 to be split. Thelength of the blade preferably is such that the entire outer offsetedges 26, 28 thereof project through the board.

In accordance with the preferred embodiment of the present invention thespaced cutting edges 22, 24 formed on the leading edge of the blade areparallel for a length at least equal to the thickness of the board to besplit, and the lateral sides of the remaining outer portion of the bladeto the outer offset edge 28 converge outwardly to reduced thickness.Thus, the outer portions 22 and 24 of the spaced cutting edges 22, 24converge outwardly and taper slightly rearward. The convergence andtaper preferably are arcuate, as illustrated, since it has been foundthat an even smoother kerf surface is produced by such arcuate form ascompared with a rectilinear taper.

As best shown in Figures 2 and 3, a substantially uniform width ismaintained from the outer ends of the cutting edges 22', 24' of theblade rearwardly along the oblique outer edge 28 to a point on theintermediate undercut 30 which corresponds with the maximum cuttingcircle 36 of the leading edges 22', 2,4. The width of the undercut 30preferably then converges outwardly to the saw tooth edge 32. Since thewidth at the outer ends of the cutting edges 22, 24' is notsubstantially greater than the maximum cutting width of the saw tooth,said edges are protected against breaking and premature dulling. Theouter oblique edge 26 tapers substantially uniformly rearward from thesaw tooth.

Further in accordance with the preferred embodiment of the presentinvention, the lateral sides of the splitter knife blade are hollowground in the direction of the trailing and leading edges. This performsthe two-fold function of minimizing friction between the blade and thewood being cut, and also facilitates sharpening of the blade withmaximum precision and speed.

The operation of the splitter knife of the present invention is asfollows: As a board is fed toward the rotating splitter knives mountedat spaced intervals about the circumference of a splitter knife head,the saw tooth 32 first engages the wood and cuts away an initial kerfhaving a maximum thickness corresponding to the maximum width of the sawtooth projecting beyond the radius 36. The wood is removed in the formof sawdust. The wood adjacent the kerf then is engaged by the outertapered sections 22', 24' of the spaced cutting edges, whereupon thewood is removed progressively in the form of fine shavings, until thekerf has been widened to the maximum width of the blade defined by theparallel sections of the spaced cutting edges 22, 24. The action of theouter arcuately tapered portions of the spaced cutting edges is similarto a jack plane, whereupon the kerf surfaces thus produced are finishedwith a smoothness equal to the remaining planed surfaces of the board.

The provision of the outwardly converging spaced cutting edges 22, 24'at the outer end of the splitter knife blade affords the additionaladvantage of retaining the sharpness of said cutting edges, thereby notonly necessitating fewer sharpenings and hence fewer periodsofinterrupted production, but also extending substantially the useful lifeof the splitter knife.

It will be apparent to those skilled in the art that variousmodifications and changes of the structural details describedhereinbefore may be made without departing from the scope and spirit ofthis invention. For example, each of the lateral sides of the outer endof the blade may be tapered on a single rectilinear or arcuate plane.Alternatively the taper may be confined to the area adjacent the edge28. Still further, the area adjacent the intermediate edge 30 may betapered from maximum width at the saw tooth edge 32 to minimum width atthe juncture with edge 28, it being required however that the width atthe saw tooth edge 32 be not substantially greater and preferably less,than the width at the outer ends of i the tapered cutting edges 22', 24.Accordingly, it is to be understood that the foregoing description isprimarily illustrative of the invention and is not to be considered aslimiting the scope thereof.

The splitter knife of this invention overcomes all of the disadvantagesof splitter knives of prior construction. It affords the production ofkerf surfaces which are as smooth as can be produced by the bestplaners, and at a lumber feed rate of more than twice the feed rateheretofore possible with. prior splitter knives. A set of the knives iscapable of splitting more than ten times the number of board feet oflumber than is possible with a set of knives .of prior construction;

Having now describedmy invention and the manner in which the same may beused, what I claim as new and desire to secure by Letters Patent is:

1. A rotary splitter knife comprising a blade having an elongatedleading edge and tapering to reduced thickness at the trailing edge, a.saw tooth on the outer end of the blade projecting outwardly beyond themaximum cutting circle of the leading edge and trailing the latter, andlaterally spaced cutting edges projecting from the sides of the leadingedge in the direction of rotation of the knife, a radially inwardportion of the cutting edges being longer than the, thickness of a boardto be splitv and the lateral spacing thereof being greater than thecutting width of the saw tooth, the lateral spacing of the cutting edgesat, their inner, working ends being at least equal tovthe lateralspacing a distance radially outward therefrom at least equal to thethickness of a board to be split, the; outward portion of the cuttingedges thereby projecting through a board when the blade is perpendicularthereto, the outward portion of the cutting edges converging radiallyoutward to a width not substantially exceeding the cutting width of thesaw tooth to provide planing edges which shave the board to full kerfwidth.

2. The splitter knife of claim 1 wherein said cutting edges aresubstantially parallel from their inner working ends outward for adistance at least equal to the thickness of a board to be split.

3. The splitter knife of claim 1 wherein the working length of saidleading edge is concave across its lateral dimension, thereby definingsaid laterally spaced radially extending cutting edges.

4. The splitter knife of claim 1 wherein the spaced cutting edges .ofsaid outer portion of the blade converge radially and arcuately outwardto a terminal width substantially equal to the greatest cutting width ofthe saw tooth- References Cited in the file of this patent UNITEDSTATES, PATENTS 347,008 Proctor Aug. 10, 1886 528,602 Little Nov. 6,1894 1,125,102 Huther Jan. 19, 1915 1,628,724 Hoffman May 17, 19271,786,959 Orr Dec. 30, 1930 1,988,898 Hafner Jan. 22, 1935 2,160,525Thornton May 30, 1939 2,285,315 Thompson June 2, 1942 FOREIGN PATENTS185,210 Switzerland Oct. 1, 1936

